Hall-Petch law and hardness-yield strength correlation
Hall-Petch law and hardness-yield strength correlation
(OP)
Hello everyone!
I have a question:
I am currently working on an austenitic steel and after applying Hall-Petch law, the slop of a curve (on HV vs d^-1/2 graph) is different than taken from the literature... How can I explain this? May it be connected with "k" coefficient?
Another question:
There is a well known law for metals, connecting hardness and yield strength:
H = α x YS
α for metals should be around 3... But it's not working once again in my case - it's about 1,2. How can I explain this?
I would be grateful for any indications!
I have a question:
I am currently working on an austenitic steel and after applying Hall-Petch law, the slop of a curve (on HV vs d^-1/2 graph) is different than taken from the literature... How can I explain this? May it be connected with "k" coefficient?
Another question:
There is a well known law for metals, connecting hardness and yield strength:
H = α x YS
α for metals should be around 3... But it's not working once again in my case - it's about 1,2. How can I explain this?
I would be grateful for any indications!





RE: Hall-Petch law and hardness-yield strength correlation
The arbitrary 0.2% offset value does not have a theoretical basis, it is an engineering convenience.
This is especially true in low strength, high work hardening alloys.
I have only ever seen these relationships used for alloys that have a high yield strength and large elastic region.
= = = = = = = = = = = = = = = = = = = =
Plymouth Tube
RE: Hall-Petch law and hardness-yield strength correlation
RE: Hall-Petch law and hardness-yield strength correlation
I cannot recall having learned such a relationship, certainly not for austenitic SS.
Are you working on steel or an assignment?
"If you don't have time to do the job right the first time, when are you going to find time to repair it?"
RE: Hall-Petch law and hardness-yield strength correlation
Also, the Hall-Petch relationship is between the yield strength and grain size, not hardness or ultimate tensile strength.
RE: Hall-Petch law and hardness-yield strength correlation
RE: Hall-Petch law and hardness-yield strength correlation
= = = = = = = = = = = = = = = = = = = =
Plymouth Tube
RE: Hall-Petch law and hardness-yield strength correlation
Do you have any suggestions have can I explain that my slope of H-P law is different that in the articles? It means that I obtained higher values of hardness for the approximately same grain size (for the samples in the same thermomechanic state).
RE: Hall-Petch law and hardness-yield strength correlation
Also for a high work-hardening FCC metal (austenitic), any cold work will increase yield strength without decreasing grain size. You could simply have cold-worked material and the paper you have uses solution annealed material.
RE: Hall-Petch law and hardness-yield strength correlation
RE: Hall-Petch law and hardness-yield strength correlation
RE: Hall-Petch law and hardness-yield strength correlation
Flow stress in shear, k. Definitely not arbitrary offset value.
If k = Y/√3, then applied pressure during hardness testing is p = 3Y, where Y is yield stress.
RE: Hall-Petch law and hardness-yield strength correlation
To summarize, predicting the results after the heat treatment would require knowledge of many more variables than you have provided so far. This is the reason for testing to verify properties after heat treatment.